1. Field of Invention
The invention relates to a method for generating and updating data for use in a destination-tracking system consisting of at least one mobile unit in accordance with claim 1 as well as a device for carrying this out in accordance with claim 38.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Navigational or destination tracking systems have recently been attracting significant attention, particularly their application in motor vehicles. The purpose of such systems lies in guiding a driver to a target destination by electronic aids after the destination has been entered by the driver. Firstly, the route can be found accurately without tiresome questioning of third parties and secondly, congestion or other traffic obstructions can be avoided.
Typical navigational systems work by continuously analyzing the current location of a moving vehicle and comparing this position with a road network in the form of geographical data. This information can be read from a road map stored, for example, on a CD-ROM carried in the vehicle. From the geographical data and assumptions about achievable speeds, a computer determines a favorable way to a destination possibly or optionally taking into account additional specific road information such as reports of road works, accident reports, etc., transmitted by communication systems. The result is shown by means of a display, for example represented graphically in the form of a map, in which the location of the vehicle is indicated, e.g., by a point. On the basis of the map displayed together with the current location of the vehicle, the driver can follow the displayed route up to the destination node. Such a system or method is described, for example, in DE 35 12 127 A1.
Similarly, DE 38 28 725 A1 describes a method to record and store a route carried out for the first time with a facility installed in the subject vehicle. When making a new trip along the same route, this recorded information can be reused. This method is intended to simplify the requirements, described in DE 35 12 127 A1, of comparing the current location of the vehicle with stored geographical data for a route which is already known to the subject vehicle. DE 41 05 180 A1 describes an autonomous road guiding system for motor vehicles which contains a device to record the course of a street actually taken and stores the data in a storage unit. Impulses along the route are detected automatically, whereas changes of direction are entered by hand via the push-buttons of the device or via the direction indicator of the vehicle. The storage unit thus programmed can be taken out of the device and given to a third party thus making it possible for the third party to drive along an unknown route with the help of the storage unit. One of the problems of this autonomous road guiding system, among others, is that only quite specific road topologies can be saved and updates are not carried out. Thus neither changes in the road topology nor unexpected events between the programming of the storage unit and the trip of the third party are taken into account. Additional problems are encountered in the xe2x80x9ccalibrationxe2x80x9d of the geographical data.
In addition to the above, DE 40 08 460 A1 describes a method which takes into account the current traffic conditions when selecting a route. The current traffic condition data is transmitted to the destination tracking device in the vehicle in the same way which makes it now possible for vehicles with radio sets to receive radio traffic news.
DE 43 34 886 A1 describes a destination tracking device for motor vehicles with an on-board computer which extracts and processes signals for a route to a given trip destination said to be optimal with regard to travel time and/or fuel consumption. The vehicle contains a facility which has collected and stored data on the time-dependent occurrence of traffic obstructions during at least one earlier information gathering trip. Said data are entered into an on-board computer and taken into account when determining a modified route. The well known destination tracking device mentioned above has the advantage that it is not dependent on external facilities such as radio traffic services or computers to record traffic hold-ups. However the data entered to identify traffic obstructions is seldom up to date. The geometric route section data, furthermore, is taken automatically from a CD-ROM and consequently is not always up to date.
U.S. Pat. No. 4,350,970 A1 describes a method for recording the travel time of a vehicle between two given nodes, and for transmitting said travel times to a computer designated as the master computer. Said master computer then compares the travel times with average values; if there are significant deviations, another route is proposed to subsequent vehicles. The transmitting vehicle does not receive the revised result. In other words it is a traffic control system and not a destination tracking system.
DE 195 26 148 C2 and DE 195 34 589 A1 describe methods as well as systems for forecasting traffic flows. The basic structure corresponds to the method and system discussed earlier in DE 35 12 127 A1. But in contrast to the method and system disclosed in DE 3512127 A1, the method and system described in DE 195 26 148 C2 successively stores the momentary vehicle speed and its current position which are continuously determined by means of a receiver tracking signals from a navigational satellite system, said receiver being located in a storage unit in each vehicle of a sampling fleet. The stored locations are part of the trip route data which are transmitted time-dependently and/or route-dependently by the sampling vehicle to a traffic control computer. Simultaneously xe2x80x9ccurrent trip activity dataxe2x80x9d from stationary sensors is also transmitted to the central computer. The central computer then analyses the transmitted route and trip activity data against a stored digital road map and determines the traffic volumes, i.e. the vehicles per time unit at a specific road cross section based on that route data. Subsequently, according to DE 195 34 589 A1, traffic development can be forecast by the central computer from the stored traffic volumes. It is reported that the central computer can propose xe2x80x9ctime-optimalxe2x80x9d routes to other road users based on this forecast and its stored digital road maps. The title of DE 195 26 148 C2 not withstanding, traffic flows cannot be forecast by these known methods or systems since the most important information requirement, namely the start and destination nodes of the vehicles, are not known by the central computer. Furthermore, the corresponding linear equation system always exhibits an arbitrary degree of incorrectness.
The systems or methods described in DE 35 12 127 A1, DE 38 28 725 A1 , DE 40 08 460 A1, DE 195 26 148 C2 and DE 195 34 589 A1 have one thing in common, they all use a static database with regard to the geographical data. An exchange of the geographical data is carried out only from time to time. Even a short time after the geographical data of a certain region has been fed into the storage device of a vehicle, it may no longer be up to date since, for instance, a route or link may be blocked, or newly opened, or the travel direction in a one-way street may have changed. Furthermore, these known systems or methods do not take into account the fact that the same route may exhibit different travel times at different times of day, traffic conditions, weather conditions, etc. Another inherent property of these conventional systems is that the destination is addressed by input of the name of the location together with the name of the road and, sometimes, a street number. If the destination node in this format is not known to the system it is impossible to calculate any route.
Furthermore, these known methods and systems are based on the hypothesis that the available road network is essentially known. In fact, however, the geographical data actually stored represents reality only incompletely, with the degree of incompleteness varying from region to region.
The effort necessary to maintain updated information on the accessible route network is both highly time consuming and costly. It is also not feasible to operate in all parts of the world with the same standard. Updating of data is always incomplete and prone to errors and can be carried out only after a significant delay in time. The updated data can be made available to the user only after a significant delay in time.
Since the known methods and systems only have subsets of the actual route network available, the route recommendations might involve considerable detours (with respect to length and time). If for example, an apparently unimportant part of the road network, particularly if it lies in the direct direction to the destination node, is unknown to the system, it may cause a significant delay to the vehicle requesting a route recommendation.
The effect of driving along detours can easily take on considerable significance considering that this fault applies to all mobile units.
It is an object of the invention to establish a method to generate appropriate data utilizable for a practical destination tracking system which carries out a permanent self updating and with data generation which requires little effort. The method is also appropriate for deriving destination tracking data from the data generated in accordance with the aforesaid method.
It is another object of the invention to provide a device for carrying out the method described above.
As far as the method is concerned, the object of the invention is attained by the characteristics of claim 1. Additional advantages resulting from the method of the invention are specified in dependent claims 2 to 37.
The method of the invention is characterized by the fact that in a mobile unit, e.g. a motor vehicle, traveled distance data are generated and are used for automatically generating a digital route network which maps the sections of the route that the mobile unit has covered. This network information is then saved in a storage device. This route network is stored as a section data file which contains the individual route sections with their initial and end points. By means of the continuous extension and/or updating of the section data file with new section data generated for new sections traveled by the mobile unit, the route network corresponds, step by step, to the conditions of the real route network so that, at any point in time, there is a current route section network available to the mobile unit.
In addition to the geographical coordinates xi, yi, of the points Pi, the direction of movement xe2x88x9di of the mobile unit can be recorded when generating the traveled distance data. The direction of movement xe2x88x9di can either be derived from the geographical coordinates xi, yi, of the points Pi of the traveled distance data or be detected by means of at least one sensor unit provided for the mobile unit.
To avoid unnecessary overburdening the storage device provided in the mobile unit, additional provisions can be made to permit the generation of traveled distance data and/or section data to be interrupted if the newly generated data already exist in the storage device of the mobile unit, and to cause said generation to be restarted if the newly generated data have not yet been stored in the storage device of the mobile unit.
Since the section data file stored in the mobile unit is continuously extended and/or updated, a highly topical route recommendation can be presented, at any time, if so requested by entering a desired point of destination and possibly a starting point for the mobile unit into an input device contained therein, provided the mobile unit contains a data processing device. If the starting point is already known, it does not need to be entered. The suggested route is presented visually and/or acoustically.
The provision of at least one central computer, separate from the at least one mobile unit, as set out in claim 7, makes it possible to merge the section data files created by several mobile units into at least one overall route file which gives a complete view of the utilizable and used road network. In order to keep the required storage capacity of the central computer to a minimum, provisions can be made so that a central computer checks a section data file transmitted by a mobile unit for its update value before merging the new section data files and only merges those section data files which have been recognized as at least partially new into the overall route file. According to the characteristics of claim 9, it is possible to build up different overall route files for different types of mobile units, for example special files for cars, lorries, motorcycles, cars of various size or type of motor, etc. Other criteria, attached for example to the user of the mobile unit (age, sex, etc.), can also be taken into account for the construction of various types of overall route files. Such type specific files permit the selection of the most favorable route for each category of users.
According to the method of the invention, data collection is fully automatic. Collection of data can of course be switched off from within the mobile unit. If the individual participants are hesitant to have their personal data transmitted to a central computer, then according to claim 10, it may be advantageous to pay for data transmitted by participant to a central computer in order to achieve optimal data collection. The amount of the reimbursement fee can be determined in accordance with the update value of the data.
The communication between the mobile unit and a central computer can be achieved in various ways. The data recorded by the mobile unit can be transmitted to the central computer automatically upon reaching the end of a movement, for example defined as reaching the point of destination, or if requested by the central computer either periodically or in accordance with any other criterion. Given that a mobile unit is fitted with adequate devices, communication between a central computer and a mobile unit can occur alternatively automatically, after a given time period, or upon request by the mobile unit, as a function of the update value of the item of new information to be transmitted, or in accordance with other criteria.
Besides an optional processing device in the mobile unit, a central computer can also propose and transmit to a mobile unit, if so requested by said mobile unit specifying a starting point and a destination point, a proposed route on the basis of the at least one overall route file already stored in the central computer.
Frequently the existing section data file and/or overall route file does not contain the desired origin and/or destination point requested by the mobile unit. In such case, to compute a proposed route, it is recommended that an optional data processing device in the mobile unit or a central computer use the nearest known origin and/or destination point from the section data file stored in the mobile unit or from the at least one available overall route file stored in the central computer.
Known destination tracking systems or methods, in most cases, determine the requested destination node by inputting the town""s name, the name of the street, and possibly the street number. However, if the destination node is given by its geographical coordinates, it is possible, as already discussed above, that an optional data processing unit in the mobile unit itself, or a the central computer can direct the mobile unit to a destination in close vicinity of the unknown destination node, by using known coordinates and their corresponding streets and/or street numbers. Any available (geophysical) system of coordinates can be used for this purpose.
Since the input of coordinates is difficult for the average user of such navigational systems or methods, the provision of a bar code reader as an input device to read the coordinates could facilitate the entry of data. A voice input is also possible.
In this connection, it should be noted that the destination point need not be specified by its geographical location alone but also by additional characteristics. Thus the method of the invention can also be used, e.g., to find routes to supermarkets, exhibitions, amusement parks, etc., and, for example, even a specific exhibition stand on the ground of a trade fair could be found. It goes without saying that destination data can also be merged with additional data from other information systems, e.g. informative data about the destination such as hotel data, public transport time tables, speed limits, etc.
A further measure to reduce the requirements of storage capacity in the mobile unit or a central computer is described in claim 20, according to which the generation of traveled distance data of the mobile unit is only activated if the mobile unit does not take the route suggested by a central computer or by the data processing device in the mobile unit itself. Additionally, provision can be made to interrupt the generation of traveled distance data if the trip is interrupted.
Besides the provision explained above for recording geographical coordinates xi, yi, of the points Pi of the traveled distance data, the point in time Ti when points Pi are reached can also be recorded and stored in the storage device of the mobile unit. Furthermore, provision can be made to assign the absolute time of movement Tjk to the sections PjPk traveled. Also the actual duration of travel tjk can be assigned to the sections PjPk. By this means, the realized travel time for each individual section can be taken into account in the planning of a route. This procedure is superior to that of known technologies which assign the average speeds reached by a traffic flow on a route section or calculate travel time on the basis of the momentary speed of a sample vehicle, since using speeds to determine a recommended route with a view to the shortest travel time is inadequate both at the microscopic (one mobile unit) and the macroscopic level. Using recorded speeds (the quotient of distance and time) to calculate the required travel time for a route section is fundamentally inaccurate since the speed is constantly changing.
A description follows below on how the additional data mentioned above permit to build up a section data file and/or an overall route file, which takes into account the patterns of movement at various times on the same route sections. For the purpose of data compression and the production of data which are as meaningful as possible, the points of time Ti can be used to merge the section data for those calendar times which exhibit a similar typical movement pattern or traffic activity. This then can be taken into account in the planning of routes.
In addition, it has proven to be advantageous, if the same geographical sections, when covered during different trips of the mobile units in predetermined time periods resulting in the duration of movement tjk, are combined in the section data file so that, for instance, the durations of movement tjk, are combined in the section data file so that, for instance, the durations of movement tjk required for a given section at a given hour on the first Monday of a given month can be fetched. Average values can be calculated from the durations of movement tjk. 
The characteristics of claim 28 mean that it is possible to forecast the realizable duration of motion for a typical pattern of movement provided that no special or unusual events, such as accidents, floods, building works, etc., are present.
In determining the pure duration of motion tjk, it may be advantageous to suppress the idle time of the mobile unit during the collection of data.
claim 30 gives an example where similar traffic conditions occur during recurrent calendar periods. Generally it can be stated that traffic activity fluctuates periodically so that there are similar calendar times regarding the traffic activity, e.g., Monday morning, Friday afternoon, the start of holiday, etc. The features of claim 31 achieve the advantage that, in addition to the section data collected over a long period of time and evaluated statistically, the most recent section data are stored in a short-term section data file so that it is possible to recognize when a special event, such as a particularly slow travel speed caused by a building works, or an accident, or if the current section is part of a one-way road, etc., is present. The nodes PJPK of a route section Pj, Pk can be fixed in many different ways. They can, for example, be fixed according to the occurrence of changes of direction or because they lie at the intersection points of sections of different direction.
In order, for example, to be able to obtain further information about petrol/gas stations for mobile units, provision can be made to store additional information, such as the idle time intervals of the mobile units, in the section data. claim 36 characterizes the fundamental execution of the method for the solution of the second part of the purpose of the invention. For example, the section file, which models the total traffic activity, permits to calculate, reliably and with a high level of topicality, a route from a given starting point to a given point of destination, thus minimizing the duration of motion or the length of the route.
The features of claim 37 make additional improvements to the precision of the method in generating destination tracking data. generating destination tracking data.
The computer cited in claims 36 and 37 could either be a data processing device in the mobile unit or a central computer.
Concerning the device and/or the system, the above object of generating data usable for a destination tracking system is attained using the characteristics of claim 38. Claims 39 to 52 describe advantageous embodiments of the device of the invention. The device of the invention has the same advantages which have been previously explained in the description of the method of the invention.
To facilitate inputting address information, an input device can be provided that reads address information from a data storage medium. This data carrier can, for example, be a visiting card containing the address information. Said facility can also be a bar code reading device or a speech input device.
It should be noted that the term xe2x80x9cmobile unitxe2x80x9d covers not only vehicles but also, for example, pedestrians who are equipped with a portable navigational system in accordance with the invention. Such a system could be advantageous, for example, to a pedestrian, if the names of roads in a city are not available or if the names are written in characters which are not decipherable by the user of the system.
If the mobile unit is a motor driven mobile unit such as a motor car, then the evaluation of the recorded basic data can be improved if the recording unit also includes means for registering the motor revolutions and the fill level of the storage unit for the energy utilized by the engine of the mobile unit, in particular the petrol tank, and for recording the temperature and/or humidity, etc. The accuracy of the evaluation of the data can be further improved by these means since the motor revolutions can be used as an indication of how often the vehicle had to halt at traffic lights and the level of the tank contents can be used to determine where a suitable petrol station is available since the tank""s state between empty and full is recorded.
A gyrometer or a compass can be provided to register the direction of movement of the mobile unit. The device for recording the respective absolute position might also be a GPS receiver. In order to reduce the amounts of data required by a central processing unit for the fulfillment of its tasks, it can be advantageous to connect several regional stationary central computers in a network instead of installing a single stationary central computer.
Summarizing, the travel destination tracking data can be calculated from the overall route file after the input of both origin and destination nodes as well as the intended travel time. Since all origin-destination relationships of the traffic or the actual movements of the mobile units in relationship to all possible parameters are known, it is possible to give destination route recommendations for all traffic participants in such a way that the sum of time for the movements of all participants is minimal.